Folded or nonfolded fluorophores incorporating naphthalene:Their fluorescent quenching driven by charge transfer or co-aggregation in the aqueous-organic binary solvent

Folded or nonfolded fluorophores incorporating naphthalene were synthesized and characterized by steady state fluorescence technique.Paraquat as an excellent quenching reagent quenched the fluorescence of Nel6 or nDs(n = 1-4) driven by charge transfer.Under aggregation of nDs,α-CD did not quench the fluorescence of 1D.At lower concentration,the quenching tendency ofα-CD against nDs is 2D>3D>4D,while at higher concentration,the tendency is 2D<3D<4D.α-CD showed the selective recognition on its flu...

THE SYNTHESIS OF Ag-POLYPYRROLE NANOCOMPOSITE COATED LATEX PARTICLES AND THEIR APPLICATION AS A FLUORESCENT QUENCHING AGENT

Submicron-sized Ag-polypyrrole/poly（styrene-co-methacrylic acid） （Ag-PPy/P（St-co-MAA）） composite particles were fabricated via a redox reaction between pyrrole and AgNO3 in the presence of P（St-co-MAA） soap-free latex. The products are characterized by transmission electron microscopy （TEM）, electron diffraction spectra （EDS）, Raman spectra, thermogravimetric analysis （TGA） and scanning electron microscopy （SEM）. The results showed that Ag-PPy nanocomposites were in situ deposited onto the surface of P（St-co-MAA） latex particles tailored by carboxylic-acid groups. The nanocomposites of Ag-PPy distributed on the surface of polymer particles transformed from discretely dots to continuously coating as the reaction temperature increased from 15℃ to 60℃. Strawberry-like composite particles were obtained at the reaction temperature of 60℃. The TGA characterization confirmed that the Ag-PPy nanocomposites loading onto the P（St-co-MAA） particles were systematically controlled over a range of 6 wt%-42 wt% by changing the reaction temperatures. The fluorescence quenching effect of the Ag-PPy/P（St-co-MAA） composite particles was explored on Rhodamine B as a model molecule with the Stern-Volmer quenching constant Ksv of 5.9 × 104 （g/mL）-1. It is suggested that the fluorescence quenching effect is caused by the resonance energy transfer mechanism.

Luminescence Quenching Behavior of Oxygen Sensing ORMOSIL Films Based on Ruthenium Complex

An organically modified silicate(ORMOSIL) based optical sensor response to gaseous O2 or O2 dissolved in water is presented. The oxygen sensing film mechanism is based on the principle of fluorescence quenching of tris(4,7-diphenyl-l , 10-phenanthroline) ruthenium ( ) ([Ru(dpp)3]2+), which has been entrapped in a porous ORMOSIL film. In order to establish optimum film-processing parameters, comprehensive investigations, including the effects of the polarity and the hydrophobicity of the sensing film on oxygen quenching response and response time, were carried out. The film hydrophobicity increased as a function of dimethyl-dimethoxysilane (DiMe-DMOS) content, which is correlated with enhanced oxygen sensor performance. The sensor developed in the present work exhibits the advantages of fast response time and good reversibility. The detection limits are 0. 5 % and 0. 3 g/mL for O2 in the gaseous and the aqueous phases, respectively.

Fluorescence quenching method for the determination of catechol with gold nanoparticles and tyrosinase hybrid system

The determination method of catechol by fluorescence quenching was developed.The assay was based on the combination of the unique property of gold nanoparticles with tyrosinase enzymatic reaction.In the presence of tyrosinase,the fluorescence of gold nanoparticles was quenched by catechol which can be employed to detect catechol.Under the optimal conditions,a linear range 5.0×10^(-7)-1.0×10^(-3) mol L^(-1) and a detection limit 1.0×10^(-7) mol L^(-1) of catechol were obtained.o-Quinone intermediate produced...

A carbon nanoparticle-peptide fluorescent sensor custom-made for simple and sensitive detection of trypsin

Herein,we report a novel sensor to detect trypsin using a purpose-designed fluorescein-labelled peptide with negatively charged carbon nanoparticles(CNPs)modified by acid oxidation.The fluorescence of the fluorescein-labelled peptide was quenched by CNPs.The sensor reacted with trypsin to cleave the peptide,resulting in the release of the dye moiety and a substantial increase in fluorescence intensity,which was dose-and time-dependent,and trypsin could be quantified accordingly.Correspondingly,the biosensor has led to the development of a convenient and efficient fluorescent method to measure trypsin activity,with a detection limit of 0.7 mg/mL.The method allows rapid determination of trypsin activity in the normal and acute pancreatitis range,suitable for point-of-care testing.Furthermore,the applicability of the method has been demonstrated by detecting trypsin in spiked urine samples.

Fluorescence Quenching of a Novel Eu(Ⅲ) Coordination Compound for the Detection of Trace Amounts of Water： Synthesis, Structure and Photoluminescent Property

A novel luminescent coordination compound Eu（TTA）3（DEDAF）（1, TTA = 1,1,1-trifluoro-3-（2-thenoyl）acetone, DEDAF = 9,9-diethyl-4,5-diazafluoren） has been synthesized and fully characterized by infrared spectrum, elemental analysis, UV-vis spectrum, etc. X-ray single-crystal diffraction analysis reveals that compound 1 shows a mononuclear structure with the europium atom in coordinating to one DAF and three TTA ligands. The mononuclear structure units are assembled into a 3-D polymer by hydrogen bonds and π-π interactions. Photoluminescent property of 1 was investigated in detail at room temperature. Complex 1 emits strong red luminescence. However, it could be quenched even by small amount of water. The fluorescence intensity at 614 nm decreases linearly with the water content increasing（vol% in acetonitrile） in the range of 0.025~0.2% under 278 nm excitation. Thermogravimetric analysis has also been studied, which demonstrates good thermal stability of 1.

Fluorescence Quenching of Anthracene by N,N-Diethylaniline and Phenothiazine in Triton X-100/n-C_(10)H_(21) OH/H_2O Microemulsion

The photo-induced electron transfer reactions of anthracene with N,N -diethylaniline(DEA) and phenothiazine(PTZ) occur in the membrane phase of a Triton X-100/ n -C 10 H 21 OH(1-decanol)/H 2O microemulsion. DEA and PTZ exist in the membrane phase of the microemulsion. Anthracene exists in the oil continuous phase of the W/O microemulsion and in the oil core and membrane phase of the O/W microemulsion.

FLUORESCENCE AND ITS ENHANCEMENT OR QUENCHING OF Eu(TTA)_3 Phen LB FILMS

For the first time, LB films containing Eu(TTA)3Phen are obtained by using composite subphase. Eu(TTA)3Phen itself is dimcult to be transferred onto solid substrate.mixed or alternate LB films are prepared. Hydrogen bonds form between Eu(TTA)3Phen and AA or TPP(-COOH). TOPO and SB have a fluorcscence enhanGement effect on Eu(TTA)3Phen. TPP(-COOH) and Fc have a fluorescence quenching effect on it.

Spectroscopic Characterization of Eu-Enoxacin-Phen Complexes and Determination of ATP by Fluorescence Quenching

The complex of Eu 3+ and Enoxacin(ENX) and Phen was synthesized. Its compositions is Eu(ENX)_3(phen)Cl_3·2H_2O. Its fluorescence spectra were studied. The results show that the strong fluorescence emitting of 592 and 616 nm for Eu 3+ in the Eu(ENX)_3(phen)Cl_3·2H_2O complex is related to the transitions 5D_0-7F_1 and 5D_0-7F_2 respectively. A sensitive method for the determination of adenosine triphosphate(ATP) by fluorescence quenching is proposed. The method is based on the ability of ATP to inhibit the formation of a strong fluorescent complex of Eu(ENX)_3(phen)Cl_3·2H_2O. In conditions of pH 6.7 in HAc-NaAc buffer and λ_ ex=340 nm and λ_ em=616 nm, the linear range of the determination is 0.4～ 10 μg·ml -1 and the detection limit is 0.034 μg·ml -1 for ATP. The method was applied to determine ATP in adenosine disodium triphosphate injection samples with relative standard deviation of 212% and recovery of 94.8%～1037%.

Synthesis and Fluorescence of Eu-Ibuprofenum-Phen Complex and Determination of ATP by Fluorescence Quenching of Complex

The complex Eu(IB)_3(phen)·2H_2O was synthesized. The results show that the strong fluorescence emitting of 593 and 615 nm for Eu^(3+) in the Eu(IB)_3(phen) complex is related to the transitions (()~5D_0-()~7F_1) and (()~5D_0-()~7F_2,) respectively. A sensitive method for the determination of adenosine disodium triphosphate (ATP) by fluorescence quenching is proposed. The method is based on the ability of ATP to inhibit the formation of a strong fluorescent complex of Eu(IB)_3(phen). In conditions of pH 6.7 HAc-NaAc buffer, λ_(ex)=273 nm and λ_(em)=615 nm, the linear range of the determination was 0.1～10 μg·ml^(-1) and the detection limit was 0.03 μg·ml^(-1) for ATP. The method has been applied to determine ATP in adenosine disodium triphosphate tablets samples with relative standard deviation of 2.18% and recovery of (98.4%～)104.0%.

Aggregation-dependence of Optical Properties and Fluorescence Quenching of a Water-soluble Poly(phenylene ethynylene)

The solvent and surfactant-dependent aggregation behaviors of the anionic poly（phenylene ethynylene） were studied and used to tune optical properties and fluorescence quenching efficiency.

Mechanisms of Fluorescence Quenching of Pr^(3+)-Doped PbWO_4 Crystal

Fluorescence decay curves of the ^3P0 and ^1D2 manifolds in Pr^3＋ doped PbWO4 crystal were measured at room temperature and fluorescence lifetimes of both manifolds were estimated. Combining with the radiative lifetimes of the manifolds calculated on the basis of the modified J-O theory, the main mechanisms for the fluorescence quenching of the manifolds were analyzed. The multi-phonon relaxation and the cross-relaxation energy transfer are the major reasons for the fluorescence quenching of the ^3P0 and ^1D2 manifolds, respectively. The Inokuti-Hirayama model was used to analyze the fluorescence decay curve of the ^1D2 manifold and the cross-relaxation of dlpole-dipole interaction was confirmed. Consequently, the ^3p0 manifold is more favorable as an upper laser level than the ^1D2 manifold.

Amplified Detection of Iron Ion Based on Plasmon Enhanced Fluorescence and Subsequently Fluorescence Quenching

A facile and rapid approach for detecting low concentration of iron ion(Fe3+) with improved sensitivity was developed on the basis of plasmon enhanced fluorescence and subsequently amplified fluorescence quenching.Au1Ag4@Si O2 nanoparticles were synthesized and dispersed into fluorescein isothiocyanate(FITC) solution. The fluorescence of the FITC solution was improved due to plasmon enhanced fluorescence. However, efficient fluorescence quenching of the FITC/Au1Ag4@Si O2 solution was subsequently achieved when Fe3+, with a concentration ranging from17 n M to 3.4 l M, was added into the FITC/Au1Ag4@Si O2 solution, whereas almost no fluorescence quenching was observed for pure FITC solution under the same condition. FITC/Au1Ag4@Si O2 solution shows a better sensitivity for detecting low concentration of Fe3+compared to pure FITC solution. The quantized limit of detection toward Fe3+was improved from 4.6 l M for pure FITC solution to 20 n M for FITC/Au1Ag4@Si O2 solution.

Laser-Induced Recoverable Fluorescence Quenching of Perovskite Films at a Microscopic Grain Scale

Understanding the fundamental properties of metal-halide perovskite materials is driving the development of novel optoelectronic applications.Here,we report the observation of a recoverable laser-induced fluorescence quenching phenomenon in perovskite films with a microscopic grain-scale restriction,accompanied by spectral variations.This fluorescence quenching depends on the laser intensity and the dwell time under Auger recombination dominated conditions.These features indicate that the perovskite lattice deformation may take the main responsibility for the transient and show a new aspect to understand halide perovskite photostability.We further modulate this phenomenon by adjusting the charge carrier recombination and extraction,revealing that efficient carrier transfer can improve the bleaching resistance of perovskite grains.Our results provide future opportunities to attain high-performance devices by tuning the perovskite lattice disorder and harvesting the energetic carriers.

Synthesis and Fluorescence Quenching of Copolymer Containing3, 4, 9, 10-Perylenetetracarboxyl Diimide Side Chains

A photoluminescence material, copolymer of N-vinylcarbazole (VCz) and N,N'- bisallyl-3, 4. 9, 10-ferylenetetracarboxyl diimide (APTC) chromophores P(VCz-APTC) was synthesized. The fluorescence quenching of P(VCz-APTC) by fullerene (C-60) and triethylamine was also studied.

Study on State of Terbium Ion in Liposome by One order Derivative Fluorescence Quenching Method

The state of Tb3+ is investigated in liposome. When the concentration of PC is below CMC (critical micell concentration), most of Tb3+ is associated with PC, the binding constant is about 3.35×103 L/mol. When the concentration of PC is beyond CMC, most of Tb3+ is dimerized, the dimerization constant is about 3.92×104L/mol. In PC?CH?H2O system, the binding constant of Tb3+?CH complex 2.93×104L/mol is obtained.

A FLUORESCENCE QUENCHING IMNUNOASSAY METHOD FOR DETERMINATION OF TRACE ALBUMIN USING UNLABELED EUROPIUM CHELATE

A fluoroimmunoassay method using unlabeled europium chelate is described.The principle is similar to that of fluoroimmunoassay method using lanthanide chelate as labels.The procedure is simple because labeling process is omitted.The detection limit is about 10^(10) mol/L antigen.The relative standard deviation of immunoassay is less than 10%.The recoveries of human serum albumin and estradiol protein conjugate are 96-105% and 111% respectively.

A New Fluorescent Chemosensor for Selective and Sensitive Detection of Mn2+ in Acidic Medium

Recently, fluorescent sensors have attracted considerable attention in their sensitive and selective determination of heavy metal ions in the aqueous acidic medium due to their advantages such as low cost and easy handling. In this study, the bathocuproine (BCP) compound was used as a fluorescent chemosensor. The selectivity and sensitivity of BCP have been investigated against some metal ions of biological and environmental importance. The results obtained from the ultraviolet-visible region (UV-vis.) and the fluorescence spectroscopy experiments revealed that the BCP sensor showed selectivity and sensitivity only to Manganese (II) ions in the experimental conditions studied. In addition, the binding stoichiometry of BCP and Mn2+ was determined to be 1:1 by the Benesi-Hildebrand method.

A QUENCHING FLUORESCENCE IMMUNOASSAY METHOD FOR DETERMINATION OF TRACE ALBUMIN USING UNLABELED TERBIUM CHELATE

A fluoroimmunoassay method using unlabeled Terbium chelate is described.The principle is similar to that of fluoroimmunoassay method using lanthanide chelate as labels.The procedure is simpte because labeling process is unnecessary.The recovery of HSA and albumin in urine is 107% and 95% respectively.The standard deviation is tess than 10%.

A NEW KIND OF SURFACTANT:LONG-CHAIN ALKYLTRIPHENYLPHOSPHONIUM HALIDES Ⅲ.AN“ABNORMAL”QUENCHING OF PYRENE FLUORESCENCE BY PHOSPHONIUMS WITH DIFFERENT LENGTHS OF ALKYL CHAIN

A study of the quenching of pyrene fluorescence by a series of alkyltriphenylphosphonium bromides indi- cated the coiling conformation of ionic surfactant in aqueous solution.Formation of pyrene excimer in cetyltriph- enylphosphonium solution strengthened the conclusion.